1. Field of the Invention
The present invention generally relates to an information recording method and, more particularly to an information recording method using an information recording medium capable of recording information by exposure to energy beams, a method of reproducing the information recorded, and a system for recording and reproducing.
2. Discussion of Background
A recorded mark or domain is typically formed by irradiating a single laser beam onto a recording medium and changing the intensity of the laser beam or by changing a magnetic field to be applied to a recorded domain while maintaining the intensity of the laser beam at a fixed level.
Multilevel recording for increasing density is known. As described in Technical Digest of International Symposium on Optical Memory 2001, 2001, p. 238, the First Dye media for Multilevel Recording System, Arioka et al, and Advanced Gray Scale Recording on Phase Change Optical Disks, p 240 of the same document, the multilevel recording of a reproduction signal is effected by changing mainly the area of a recorded mark or domain.
As for the multilevel recording of a reproduction signal, it is known from Proceeding of Optical Data Storage 2000, SPIE Vol. 4090, 2000 that the multilevel recording of a reproduction signal is affected by providing recording information to a wobbled groove. This method pertains to ROM, which is mastered medium, and not used for recording.
In the above method in which a single beam is irradiated onto the medium, when the recording density is increased, the distance between recorded domains is shortened. When it becomes shorter than the thermal diffusion distance at the time of recording, a thermal interference occurs between the recorded domains. Therefore, there is limitation to the increase of recording density.
In the above method in which multilevel recording is carried out-to increase the recording density, when the size of a recorded domain is reduced to increase the density, the stability of forming a recorded domain is gradually lowered. Therefore, there is limitation to the increase of recording density as well.